Machine parameters and limitations in the EURISOL beta-beam baseline

1. Machine parameters and limitations in the EURISOL beta-beam baseline A.Fabich AB department, CERN On behalf of the Beta-beam study group http://cern.ch/beta-beam

2. Outline • Conceptual Design study • Beta-beam baseline design • Machine parameters • Ion intensities • Limitations • Production • Decay losses • Acceptance • Tune shift • Conclusions A.Fabich, CERN

3. Conceptual design study • EURISOL Design Study • Within the 6th framework program of EU • Conceptual Design Report for Beta-Beam • The baseline scenario is based • on ISOL technique • at CERN: usage of PS and SPS machines • The Beta-beam Design Study is aiming for: • A beta-beam facility that will run for a “normalized” year of 107 s • Providing an annual rate of • 2.9*1018 anti-neutrinos (from 6He at g=100) • 1.1*1018 neutrinos (from 18Ne at g=100) A.Fabich, CERN

4. Beta-beam baseline design Low-energy part High-energy part Neutrino source Ion production Acceleration Beam to experiment Proton Driver Acceleration to final energy PS & SPS Ion productionISOL target & Ion source SPS Decay ring Br= 1500 TmB = ~5 T C = ~7000 m Lss= ~2500 m 6He:g= 100 18Ne:g= 100 Neutrino Source Decay Ring Beam preparationECR pulsed Ion accelerationLinac PS Acceleration to medium energy RCS A.Fabich, CERN

5. cycle of 6He magnet cycle (abstract) Machine cycle Baseline version: • Production • 6He, 18Ne • ECR, Linac and RCS • Cycling at 10 Hertz • Accumulation in the PS • Accumulation of 20 RCS bunches (~2 seconds) • Acceleration through PS and SPS as fast as possible • gtop = 100 for both isotopes • Injection into decay ring • Merging with circulating bunches • Every 6 s for 6He and every 3.6 s for 18Ne A.Fabich, CERN

6. Ion intensities • For the design goal of 2.9*1018 antineutrinos/year 1.1*1018 neutrinos/year • Required isotope intensities: • Baseline version Typical intensities of 108-109 ions for LHC injector operation (PS and SPS) Top-down A.Fabich, CERN

7. Limitations • Isotope production • The self-imposed requirement to re-use a maximum of existing CERN infrastructure • Cycling time, aperture limitations, collimation systems etc. • The high intensity ion bunches in the accelerator chain and decay ring • Space charge • Decay losses A.Fabich, CERN

8. Ion production • 6He figures have reached the design values but no safety margin is yet provided. • 18Ne figures are more than one order of magnitude below the desired performance. • Missing factor (~25) for 18Ne production • Within baseline: • Improvement of isotope production/preparation • Possibly include an accumulation scenario at low energy • 19Ne no immediate solution (for baseline scenario) • Production rate much higher, but life time 10 times higher • Acceleration of an order of magnitude more ions • Excluded by space charge limits in the PS and SPS A.Fabich, CERN

9. Decay distribution Bunch 20th 15th 10th 5th 1st • 70% of first 6He bunch are lost before reaching decay ring • Overall only 50% (6He) and 80% (18Ne) reach decay ring • Normalization • Single bunch intensity to maximum/bunch • Total intensity to total number accumulated in RCS total A.Fabich, CERN

10. Decay losses (1) • Relative decay distribution similar for both isotopes • ~90% of all decays before entering decay ring occur in the PS • Can be translated into power losses and compared with “existing” high intensity operation … A.Fabich, CERN

11. 1st 1st 20th 20th Decay losses (2) • In the PS most losses occur at low energy • accumulation • PS: g(6He)  [1.5 ; 9.3], g(18Ne)  [2.2 ; 15.5] A.Fabich, CERN

12. Energy loss/cycle Power loss Power losses Nucleon losses compared • PS and SPS comparable for CNGS and bb operation • PS exposed to highest power losses A.Fabich, CERN

13. 1σ Physical Emittance S.Hancock Scaling from normalized rms values of 7.8µm (H) and 4.2µm (V) for 11Tm 6He ions at PS injection, then We assume the 18Ne has the same normalized emittance as the 6He because it comes from the Linac with identical βγ and is multi-turn injected into the RCS with the same geometrical set-up. A.Fabich, CERN

14. Limits due to Tune Shift S.Hancock Considering for simplicity a round Gaussian beam of fully stripped ions, the self-field incoherent (“Laslett”) tune shift is This allows upper limits on the total number of ions per shot to be estimated (taking into account unequal bunches) based on known limits at injection. We assume τb = 80% of the rf bucket duration in all cases. A.Fabich, CERN

15. Solve tune shift limit S.Hancock • Two batches from the PS instead of one. • One could also imagine deliberately blowing up the emittance to improve the situation in the downstream machine. A.Fabich, CERN

16. Conclusions • Baseline parameters fixed • Study goes now into detail of different machines and aspects • Average power losses are comparable to CNGS case (which is accepted) • PS has to stand the most demanding losses • Power losses < 3 W/m • Limits set by space charge in both the PS and SPS machines. • Main efforts will now focus on 18Ne shortfall. A.Fabich, CERN